It has come up in many discussions how the N term peak in surfactant protein D may have a dark center, and this is particularly evident when one looks at the AFM images of multimers of more than just a few trimers. Some multimers actually have a deep empty center. Only in a few dodecamers is there a sub peak in the large, prominent peak for the N term junction. I looked for that indication in all the plots of the hexamers so far and it shows up very infrequently, and the data below just sort of negate that inner subpeak as non existent. It may be highly infrequent in the dodecamers, but it is not that infrequent in multimers, and thus anytime it shows up in a dodecamer becomes important in considering just how the N term domains fit together in the multimers, and if in fact they can fit together in more than one way. So the data below is pretty uninteresting, but the image and the plot (image is 2D fast fourier tranform in gwyddion. The peak detection is made in Octave using ipeak.m M80 as the settings. Coloration of the peaks in the plot are a choice that best fits the mean number of peaks per hexamer — which was determined to be 15 (see previous data). Top image is the AFM micrograph, image filters and signal processing for plot peaks.
Mid N term peak width (N=752, trimers plotted)(N=12 dodecamers (two hexamers, four trimers).  Data below also shows each individual dodecamer…. and as mentioned, most don’t show a peak in the middle of the N term peak.